Cognitive Complexity (step 2 (and maybe 3) out of 3+): implementation!

.cargo/config

@@ -1,2 +1,5 @@
 [alias]
 uitest = "test --test compile-test"
+
+[build]
+rustflags = ["-Zunstable-options"]

.github/PULL_REQUEST_TEMPLATE

@@ -0,0 +1,28 @@
+<!--
+Thank you for making Clippy better!
+
+We're collecting our changelog from pull request descriptions.
+If your PR only updates to the latest nightly, you can leave the
+`changelog` entry as `none`. Otherwise, please write a short comment
+explaining your change.
+
+If your PR fixes an issue, you can add "fixes #issue_number" into this
+PR description. This way the issue will be automatically closed when
+your PR is merged.
+
+If you added a new lint, here's a checklist for things that will be
+checked during review or continuous integration.
+
+- [ ] Followed [lint naming conventions][lint_naming]
+- [ ] Added passing UI tests (including committed `.stderr` file)
+- [ ] `cargo test` passes locally
+- [ ] Executed `util/dev update_lints`
+- [ ] Added lint documentation
+- [ ] Run `cargo fmt`
+
+Note that you can skip the above if you are just opening a WIP PR in
+order to get feedback.
+
+Delete this line and everything above before opening your PR -->
+
+changelog: none

CHANGELOG.md

@@ -1015,6 +1015,7 @@ All notable changes to this project will be documented in this file.
 [`panic_params`]: https://rust-lang.github.io/rust-clippy/master/index.html#panic_params
 [`panicking_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#panicking_unwrap
 [`partialeq_ne_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#partialeq_ne_impl
+[`path_buf_push_overwrite`]: https://rust-lang.github.io/rust-clippy/master/index.html#path_buf_push_overwrite
 [`possible_missing_comma`]: https://rust-lang.github.io/rust-clippy/master/index.html#possible_missing_comma
 [`precedence`]: https://rust-lang.github.io/rust-clippy/master/index.html#precedence
 [`print_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#print_literal

Cargo.toml

@@ -46,7 +46,7 @@ rustc_tools_util = { version = "0.1.1", path = "rustc_tools_util"}
 
 [dev-dependencies]
 cargo_metadata = "0.7.1"
-compiletest_rs = { version = "0.3.21", features = ["tmp"] }
+compiletest_rs = { version = "0.3.22", features = ["tmp"] }
 lazy_static = "1.0"
 serde_derive = "1.0"
 clippy-mini-macro-test = { version = "0.2", path = "mini-macro" }

README.md

@@ -7,7 +7,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 298 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 299 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
 
 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
 

clippy_dev/src/lib.rs

@@ -1,5 +1,3 @@
-#![allow(clippy::default_hash_types)]
-
 use itertools::Itertools;
 use lazy_static::lazy_static;
 use regex::Regex;

clippy_lints/src/approx_const.rs

@@ -1,7 +1,7 @@
 use crate::utils::span_lint;
 use rustc::hir::*;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_tool_lint, lint_array};
+use rustc::{declare_lint_pass, declare_tool_lint};
 use std::f64::consts as f64;
 use syntax::ast::{FloatTy, Lit, LitKind};
 use syntax::symbol;
@@ -53,20 +53,9 @@ const KNOWN_CONSTS: &[(f64, &str, usize)] = &[
     (f64::SQRT_2, "SQRT_2", 5),
 ];
 
-#[derive(Copy, Clone)]
-pub struct Pass;
+declare_lint_pass!(ApproxConstant => [APPROX_CONSTANT]);
 
-impl LintPass for Pass {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(APPROX_CONSTANT)
-    }
-
-    fn name(&self) -> &'static str {
-        "ApproxConstant"
-    }
-}
-
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ApproxConstant {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
         if let ExprKind::Lit(lit) = &e.node {
             check_lit(cx, lit, e);

clippy_lints/src/arithmetic.rs

@@ -2,7 +2,7 @@ use crate::consts::constant_simple;
 use crate::utils::span_lint;
 use rustc::hir;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_tool_lint, lint_array};
+use rustc::{declare_tool_lint, impl_lint_pass};
 use syntax::source_map::Span;
 
 declare_clippy_lint! {
@@ -48,15 +48,7 @@ pub struct Arithmetic {
     const_span: Option<Span>,
 }
 
-impl LintPass for Arithmetic {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(INTEGER_ARITHMETIC, FLOAT_ARITHMETIC)
-    }
-
-    fn name(&self) -> &'static str {
-        "Arithmetic"
-    }
-}
+impl_lint_pass!(Arithmetic => [INTEGER_ARITHMETIC, FLOAT_ARITHMETIC]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {

clippy_lints/src/assertions_on_constants.rs

@@ -1,10 +1,10 @@
 use if_chain::if_chain;
 use rustc::hir::{Expr, ExprKind};
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_tool_lint, lint_array};
+use rustc::{declare_lint_pass, declare_tool_lint};
+use syntax_pos::Span;
 
 use crate::consts::{constant, Constant};
-use crate::syntax::ast::LitKind;
 use crate::utils::{in_macro, is_direct_expn_of, span_help_and_lint};
 
 declare_clippy_lint! {
@@ -29,55 +29,44 @@ declare_clippy_lint! {
     "`assert!(true)` / `assert!(false)` will be optimized out by the compiler, and should probably be replaced by a `panic!()` or `unreachable!()`"
 }
 
-pub struct AssertionsOnConstants;
-
-impl LintPass for AssertionsOnConstants {
-    fn get_lints(&self) -> LintArray {
-        lint_array![ASSERTIONS_ON_CONSTANTS]
-    }
-
-    fn name(&self) -> &'static str {
-        "AssertionsOnConstants"
-    }
-}
+declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssertionsOnConstants {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
+        let mut is_debug_assert = false;
+        let debug_assert_not_in_macro = |span: Span| {
+            is_debug_assert = true;
+            // Check that `debug_assert!` itself is not inside a macro
+            !in_macro(span)
+        };
         if_chain! {
             if let Some(assert_span) = is_direct_expn_of(e.span, "assert");
             if !in_macro(assert_span)
-                || is_direct_expn_of(assert_span, "debug_assert").map_or(false, |span| !in_macro(span));
+                || is_direct_expn_of(assert_span, "debug_assert")
+                    .map_or(false, debug_assert_not_in_macro);
             if let ExprKind::Unary(_, ref lit) = e.node;
+            if let Some(bool_const) = constant(cx, cx.tables, lit);
             then {
-                if let ExprKind::Lit(ref inner) = lit.node {
-                    match inner.node {
-                        LitKind::Bool(true) => {
-                            span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
-                                "assert!(true) will be optimized out by the compiler",
-                                "remove it");
-                        },
-                        LitKind::Bool(false) => {
-                            span_help_and_lint(
-                                cx, ASSERTIONS_ON_CONSTANTS, e.span,
-                                "assert!(false) should probably be replaced",
-                                "use panic!() or unreachable!()");
-                        },
-                        _ => (),
-                    }
-                } else if let Some(bool_const) = constant(cx, cx.tables, lit) {
-                    match bool_const.0 {
-                        Constant::Bool(true) => {
-                            span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
-                                "assert!(const: true) will be optimized out by the compiler",
-                                "remove it");
-                        },
-                        Constant::Bool(false) => {
-                            span_help_and_lint(cx, ASSERTIONS_ON_CONSTANTS, e.span,
-                                "assert!(const: false) should probably be replaced",
-                                "use panic!() or unreachable!()");
-                        },
-                        _ => (),
-                    }
+                match bool_const.0 {
+                    Constant::Bool(true) => {
+                        span_help_and_lint(
+                            cx,
+                            ASSERTIONS_ON_CONSTANTS,
+                            e.span,
+                            "`assert!(true)` will be optimized out by the compiler",
+                            "remove it"
+                        );
+                    },
+                    Constant::Bool(false) if !is_debug_assert => {
+                        span_help_and_lint(
+                            cx,
+                            ASSERTIONS_ON_CONSTANTS,
+                            e.span,
+                            "`assert!(false)` should probably be replaced",
+                            "use `panic!()` or `unreachable!()`"
+                        );
+                    },
+                    _ => (),
                 }
             }
         }

clippy_lints/src/assign_ops.rs

@@ -2,7 +2,7 @@ use if_chain::if_chain;
 use rustc::hir;
 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_tool_lint, lint_array};
+use rustc::{declare_lint_pass, declare_tool_lint};
 use rustc_errors::Applicability;
 
 use crate::utils::{
@@ -53,18 +53,7 @@ declare_clippy_lint! {
     "having a variable on both sides of an assign op"
 }
 
-#[derive(Copy, Clone, Default)]
-pub struct AssignOps;
-
-impl LintPass for AssignOps {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP)
-    }
-
-    fn name(&self) -> &'static str {
-        "AssignOps"
-    }
-}
+declare_lint_pass!(AssignOps => [ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
     #[allow(clippy::too_many_lines)]